1. Field of the Invention
The present invention relates to an electrophotographic photoconductor comprising an electroconductive substrate and a photoconductive layer formed thereon comprising at least one tertiary amine compound as an effective component. In addition, the present invention also relates to a triphenylamine compound serving as a photoconductive material in the above-mentioned electrophotographic photoconductor.
2. Discussion of Background
Conventionally, inorganic materials such as selenium, cadmium sulfide and zinc oxide are used as photoconductive materials in an electrophotographic photoconductor for use with the electrophotographic process. The above-mentioned electrophotographic process is one of the image forming processes, through which the surface of the photoconductor is charged uniformly in the dark to a predetermined polarity, for instance, by corona charge. The uniformly charged photoconductor is exposed to a light image to selectively dissipate the electric charge of the exposed areas, so that a latent electrostatic image is formed on the photoconductor. The thus formed latent electrostatic image is developed into a visible image by toner particles comprising a coloring agent such as a dye and a pigment, and a binder agent such as a polymeric material.
Fundamental characteristics required for the photoconductor for use in such an electrophotographic process are: (1) chargeability to an appropriate potential in the dark, (2) minimum dissipation of electric charge in the dark, and (3) rapid dissipation of electric charge when exposed to light.
However, while the above-mentioned inorganic materials have many advantages, they have several shortcomings from the viewpoint of practical use.
For instance, a selenium photoconductor, which is widely used at present, satisfies the above-mentioned requirements (1) to (3) completely, but it has the shortcomings that its manufacturing conditions are difficult and, accordingly, its production cost is high. In addition, it is difficult to work It into the form of a belt due to its poor flexibility, and in is so vulnerable to heat and mechanical shocks that it must be handled with the utmost care.
A cadmium sulfide photoconductor and a zinc oxide photoconductor can be obtained by coating a dispersion prepared by dispersing in a binder resin cadmium sulfide particles and zinc oxide particles, respectively. However, they ore poor in mechanical properties, such as surface smoothness, hardness, tensile strength and wear resistance. Therefore, they cannot be used in the repeated operation.
To solve the problems of the aforementioned inorganic materials, various electrophotographic photoconductors employing organic materials have been proposed recently and some ore put to practical use. For example, there are known a photoconductor comprising poly-N-vinylcarbazole and 2,4,7-trinitrofluorene-9-one, as disclosed in U.S. Pat. No. 3,484,237; a photoconductor prepared by sensitizing poly-N-vinylcarbazole with a pigment of pyrylium salt, as disclosed in Japanese Patent Publication 48-25658; a photoconductor comprising as the main component an organic pigment, as disclosed in Japanese Laid-Open Patent Application 47-37543; a photoconductor comprising as the main component a eutectic crystal complex of a dye and a resin, as disclosed in Japanese Laid-Open Patent Application 47-10735; a photoconductor prepared by sensitizing a triphenylamine compound with a sensitizer pigment, as disclosed in U.S. Pat. No. 3,180,730; a photoconductor comprising an amine derivative as a charge transporting material, as disclosed in Japanese Laid-Open Patent Application 57-195254; a photoconductor comprising poly-N-vinylcarbazole and an amine derivative as charge transporting materials, as disclosed in Japanese Laid-Open patent Application 58-1155; and a photoconductor comprising as a photoconductive material a polyfunctional tertiary amine compound, in particular, a benzidine compound, as disclosed in U.S. Pat. No. 3,265,496, Japanese Patent Publication 39-11546 and Japanese Laid-Open Patent Application 53-27033.
Furthermore, there is known a photoconductor comprising as a photoconductive material a triphenylamine compound, as disclosed in Japanese Laid-Open Patent Applications 3-136057, 4-57056 and 4-282349. However, the triphenylamine compound for use in the above-mentioned photoconductor has no pyrenyl group.
These electrophotographic photoconductors have their own excellent characteristics and considered to be valuable for practical use with various requirements of the electrophotographic photoconductor in electrophotography taken into consideration, however, the above-mentioned conventional electrophotographic photoconductors cannot meet all the requirements for use in electrophotography.